#--
# Most objects are cloneable, but not all. For example you can't dup +nil+:
#
#   nil.dup # => TypeError: can't dup NilClass
#
# Classes may signal their instances are not duplicable removing +dup+/+clone+
# or raising exceptions from them. So, to dup an arbitrary object you normally
# use an optimistic approach and are ready to catch an exception, say:
#
#   arbitrary_object.dup rescue object
#
# Rails dups objects in a few critical spots where they are not that arbitrary.
# That rescue is very expensive (like 40 times slower than a predicate), and it
# is often triggered.
#
# That's why we hardcode the following cases and check duplicable? instead of
# using that rescue idiom.
#++
unless defined? ActiveSupport
  class Object
    # Can you safely dup this object?
    #
    # False for +nil+, +false+, +true+, symbol, number and BigDecimal(in 1.9.x) objects;
    # true otherwise.
    def duplicable?
      true
    end
  end

  class NilClass
    # +nil+ is not duplicable:
    #
    #   nil.duplicable? # => false
    #   nil.dup         # => TypeError: can't dup NilClass
    def duplicable?
      false
    end
  end

  class FalseClass
    # +false+ is not duplicable:
    #
    #   false.duplicable? # => false
    #   false.dup         # => TypeError: can't dup FalseClass
    def duplicable?
      false
    end
  end

  class TrueClass
    # +true+ is not duplicable:
    #
    #   true.duplicable? # => false
    #   true.dup         # => TypeError: can't dup TrueClass
    def duplicable?
      false
    end
  end

  class Symbol
    # Symbols are not duplicable:
    #
    #   :my_symbol.duplicable? # => false
    #   :my_symbol.dup         # => TypeError: can't dup Symbol
    def duplicable?
      false
    end
  end

  class Numeric
    # Numbers are not duplicable:
    #
    #  3.duplicable? # => false
    #  3.dup         # => TypeError: can't dup Fixnum
    def duplicable?
      false
    end
  end

  require 'bigdecimal'
  class BigDecimal
    # Needed to support Ruby 1.9.x, as it doesn't allow dup on BigDecimal, instead
    # raises TypeError exception. Checking here on the runtime whether BigDecimal
    # will allow dup or not.
    begin
      BigDecimal.new('4.56').dup

      def duplicable?
        true
      end
    rescue TypeError
      # can't dup, so use superclass implementation
    end
  end

  class Method
    # Methods are not duplicable:
    #
    #  method(:puts).duplicable? # => false
    #  method(:puts).dup         # => TypeError: allocator undefined for Method
    def duplicable?
      false
    end
  end
end
